I needed to install the op_video module into a Drupal install today at work, and found that the default Ubuntu install of ffmpeg won't transcode audio properly for FLV files. Here are the steps to compile FLV and create a deb package that will work properly:
apt-get install liblame-dev libfaad2-dev libfaac-dev libxvidcore4-dev liba52-0.7.4 liba52-0.7.4-dev libx264-dev liba52-dev libdts-dev libgsm1-dev libvorbis-dev libxvidcore4 libxvidcore-dev libdc1394-dev libfaac-dev liblame-dev libx264-dev libfaad2-dev libtheora-dev libsdl1.2-dev build-essential checkinstall subversion
